Port 1843: Netopia-vo5 — A Registered Port Nobody Uses

Port 1843 sits in a strange middle ground: officially registered, practically abandoned.

IANA's registry lists it as netopia-vo5, assigned to Netopia, Inc. — a broadband hardware company that made DSL modems and routers during the late 1990s and early 2000s. Motorola acquired Netopia in 2007. The "vo5" protocol was never publicly documented. No RFC was filed. No specification was published. The port was claimed and the claim was never returned.

The Registered Port Range

Port 1843 lives in the registered port range (1024-49151), sometimes called user ports. This range is where applications register port numbers with IANA so other software knows where to find them. Port 80 is HTTP. Port 443 is HTTPS. Port 1843 was supposed to be netopia-vo5.

The registered range is large — over 48,000 ports — and IANA has assigned most of the lower numbers. Many of those assignments are just as obscure as this one: products discontinued, companies acquired, protocols never standardized. The registry is partly a living system and partly a graveyard.¹

What Actually Runs on Port 1843

Almost certainly nothing intentional. If you see activity on port 1843, it is likely one of:

• A custom application that chose this port arbitrarily (common for internal tools and development servers)
• A scanner or probe sweeping ports looking for open services
• Malware using an obscure registered port to blend in with "normal" traffic

The netopia-vo5 service is not running anywhere. Netopia's products reached end-of-life and the company ceased to exist as an independent entity nearly two decades ago.²

How to Check What Is Listening

If you see traffic on port 1843 and want to know why:

On Linux/macOS:

# Show what process is listening on port 1843
ss -tlnp | grep 1843
# or
lsof -i :1843

On Windows:

netstat -ano | findstr :1843

Then take the process ID from the output and look it up:

# macOS/Linux
ps aux | grep <PID>

# Windows (Task Manager, or)
tasklist | findstr <PID>

If nothing is listening, the port is simply closed. That is the expected state.

Why This Matters

The port system works because of trust and registration. When an application says "I live on port 443," every browser in the world knows where to find HTTPS. That coordination depends on the registry being accurate and honest.

Port 1843 is a small reminder that the registry is also permanent. Ports cannot easily be unregistered and reassigned. Once a company claims a port, that claim persists in the official record long after the company and the protocol are gone.¹

If you are building a private application and need a port, pick something in the dynamic/ephemeral range (49152-65535) instead. Those ports are explicitly reserved for temporary and private use — no registration required, no chance of colliding with a legacy claim like this one.